Supply and control system for boilers and their furnaces



Dec. 22, 1936 R. N. MILLER SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES Filed July 25; 1953 9 Sheefcs-Sheet 1 INVTOR. g zrozwz 735M111, BY W TORNEYS.

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SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES Filed July 25, 1953 9 Sheets-Sheet 2 WI TNESSES: INVENTOR- liomri Nmzm,

R. N. MILLER Dec. 22, 1936.

SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES 9 Sheets-Sheet 5 Filed July 25 1953 I I N VEN TOR:

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SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES 9 Sheets-Sheet 4 Filed July 25, 1933 WITNESSES:

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Dec. 22, 1936. R. N. MILLER 2,965,285

SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES Filed July 25, 1955 9 Sheets-Sheet 5 FfGiTZT WITNESSES: I N V EN TOR W QM K006i"; N MUM;

R. N. MILLER Dec. 22, 1936.

SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES 9 Sheetg-Sheet 6 Filed July 25, 1953 FIG: II.

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WI TNESSES;

R. N. MILLER Dec. 22, 1936.

SUPPLY AND CONTROL SYSTEM FOR BOILERS AND THEIR FURNACES Filed July 25, 1935 9 Sheets-Sheet '7 I N V EN TOR: Hobart N Milly TORNEYS.

WITNESSES:

R. N. MILLER Dec. 22, 1936.

SUPPLY AND CONTROLSYSTEM FOR BOILERS AND THEIR FURNACES 9 sheets-sheets Filed July 25, 1953 I N V EN TOR:

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Patented Dec. 22, 1936 PATENT OFFICE SUPPLY AND ooNTRL SYSTEM FOR BOILERS AND THEIR FURNACES Robert N. Miller, Altoona, Pa.

Application July 25, 1933, Serial No. 682,079

16 Claims.

This invention relates to supply and control systems for boilers and their furnaces, and is hereinafter explained and described with reference to a boiler intended especially to supply steam for heating ordinary railway cars, such as day coaches, Pullmans, baggage, postal, or express cars,as when they are drawn by locomotives operated by power other than steam.

Standard passenger cars of steam railroads are equipped for steam heating, so that when they are drawn by locomotives operated by power other than steam, special provision must be made for supplying steam to heat the cars. The operation of a special boiler on a railway vehicle (as a locomotive) involves peculiar conditions which the present invention is particularly adapted to meet. Various other features and advantages that can be realized through the invention will appear from the description hereinafter of an illustrative and presently preferred form of embodiment. So far as novel over the art, all the features here shown or described are my invention.

In the drawings, Fig. I is a diagrammatic general view of a steam boiler with supply and control system or equipment conveniently embodying the invention.

Fig. II is a side view of the boiler and associated parts and equipment.

Fig. III is a fragmentary plan view, partly in horizontal section, on a larger scale than Fig. II, with a mid portion of the boiler and associated parts broken out and omitted.

Fig. IV is a plan view of the boiler and associated parts, correspondingto Fig. II, but with the water and fuel feed pumps omitted.

Fig. V is a side view of the boiler and associated parts, with the Smokestack mostly broken away, showing the side opposite that shown in Fig. II.

Fig. VI is a view from the left of Fig. IV with the boiler itself and various parts removed, showing especially the regulating equipment between the boiler and the adjacent transverse partition or bulkhead in the locomotive cab ,this partition appearing in section at the right of Figs. II, III and IV. I g

Fig. VII shows a transverse section through a feed water regulator and associated parts, taken as indicated by the line and arrows VIIVII in Fig. VI.

Fig. VIII is a fragmentary view of certain electric switches of the control system operated by the regulator of Fig. VII, the view being taken at right angles to Fig. VII, and on a larger scale,

Fig. IX is a fragmentary view of the same switches, similar to that afforded by Fig. VII but on a larger scale, with certain parts in vertical section.

Fig. X is a wiring diagram of the electrical accessories of the system and their connections, and of the control circuits for the system.

The boiler I5 here shown (see Figs. I, II and IV) is adapted to be installed on an electric locomotive as described in my co -pending application Serial No. 655,909, filed February 9, l933,--the frame of such locomotive being illustrated in U. S. Patent No. 1,828,418, granted October 20, 1931, to W. F. Kiesel, Jr. As set forth in my said application, the boiler l5 may be mounted in the locomotive cab (not shown) over water and fuel supply reservoirs in the 10- comotive frame (not shown), under the cab floor l6. (Fig. I.) Though a suitable water tube boiler might be used, the particular boiler l5 here shown is of vertical fire tube type (Fig. I), comprising outer shell I9 with upper tubesheet 20, inner shell 2| with lower tubesheet 22, and fire tubes 23 extending between the tubesheets and 22. The lower end of the boiler l5 rests on the furnace firepot 24. In the ends of the locomotive frame (not shown) are feedwater spaces or reservoirs 25, 26 connected by a siphon pipe line 21 through which water is transferred from reservoir 26 to reservoir 25 (which is the primary, direct source of supply for the boiler) by a steam siphon 28. Any excess of water thus transferred to reservoir 25 overflows and returns to reservoir 26 through a pipe line connection 29. The boiler I5 is fired by an oil burner 30 mounted at a firepot opening 3| (Figs. I, II and III). Air for combustion is supplied by a centrifugal blower 32 through a valve or dampercontrolled duct or trunk 33 that normally covers over the opening 3| and encloses the burner 30,- the blower 32 being driven by a (constant speed) electric motor 34. The products of combustion rise from the firepot 24 through the combustion space within the shell 2| and through the firetubes 23 into a vertically shallow smoke box 38 (Figs. I, II, IV and V) within the shell I9 above tubesheet 2i), closed on top by a cover 39, whence they make exit through a central opening 40 into a shallow breeching 4|. In the breeching 4|, the gases pass forward to a stack 42 offset forward of the opening M). In the smoke box 38 may be a feedwater heater and a steam superheater (not shown). Steam from the boiler dry pipe (not shown) passes through valved pipe connections 44 (Fig. II) that include the superheater (not shown) tothe train-pipe (not shown) for car heating steam.

The boiler I5 receives water (Figs. I, II, III and V) from a duplex steam driven direct-acting feed pump 45 which draws from. supply reservoir 25 through a valve and strainer-equipped pipe connection 46 and a triple fitting 41 in the top reservoir wall. The feed pump 45 delivers into the boiler I5 through pipe connections 48 that include the smoke-box feedwater heater (not shown), as well as a check valve 49. (See also Fig. V.) The feed pump 45 takes boiler steam (Figs. I, II and III) through suitably valved and controlled pipe connections 5|, to which on occasion compressed air can be supplied from a pipe 52 through a valved connection 53, in order to operate the pump before getting up steam. There is also shown (Fig. II) an emergency injector 54 that draws water from the supply reservoir 25 through pipe connections 55 including the fitting 41, and delivers to the boiler I5 through a pipe 56 with check valve 51, and also has an overflow connection 59 discharging back into the supply reservoir 25. The injector 54 takes steam from the boiler I5 through a valved connection 58 (Fig. II), which also extends up over the boiler l5 and down on the other side to the steamsiphon 28 (Fig. V).

Fuel oil is drawn (Figs. I, III and V) from a supply reservoir Ilia. under the cab floor I6 by a pump 60 driven by a constant speed (electric) motor 6|, through suction connections 62 including a double fitting 63 in the top fuel-reservoir Wall and parallel branches containing oil screens 64, 64. The fitting 93 also serves for a return connection 65 from a spring-controlled pressure-relief or by-pass valve 66 (Figs. I and V) connected to the delivery pipe connection 61 of said pump 50, leading to the burner 30. Boiler steam for atomizing is supplied the burner 30 (Figs. I, II, III and IV) through pipe connections 68, suitably valved and controlled; and air for the same purpose (before getting up steam) can be supplied to the pipe 68 through a valved connection from the pipe 52. Steam or air can also be admitted to the oil line 61 through a valved by-pass 10, for the purpose of blowing out residual oil when the boiler I5 is being shut down,so as to prevent carbonization of such oil by the heat of the furnace and consequent fouling of the burner 30.

The supply of air for combustion is controlled by an upright butterfly damper I5 (Figs. I and VI) in the blower duct 33. The supply of fuel oil to the burner 30 is controlled by a rotary stop valve 11 in the pipe line 61, and the supply of steam for atomizing the fuel iscontrolled by a rotary stop valve 18 in the pipe line 68. All of these-damper I5 and valves TI and '|8 may be operated in unison by a common actuating lever connected to their operating crank arms by link rods 8|, 82 83; and the lever 80 may be operated by a controller mechanism indicated at 85, included in the general control system hereinafter described. The controller 85 may preferably be arranged to change the air and fuel supplies from a maximum for full flame operation to give the maximum rated output of steam to'a low or minimum value just about sufiicient to maintain rated normal pres sure in the boiler I5 when no steam is being taken from it, and vice-versa.

The supply of feedwater by the feed pump 45 is preferably controlled automatically according to the water level in the boiler and the demand on the boiler for steam. For this purpose, there is a level-responsive (Copes) regulator 86 (Figs. I, II, IV, VI, and VII) comprising a thermally responsive (inclined) tube 8'! having its lower end connected to the water-space of the boiler I5 through a fitting 88 and suitably valved piping 89, and having its upper end connected to the steamspace of the boiler through a fitting 90 and suitably valved piping 9|. The fitting 88 is mounted on the lower end of a rigid frame or casing 92, and is adjustable relative to the latter by means indicated at 93; and the fitting 90 is pivotally connected at 94 to one arm of an (angular) lever 95 fulcrumed at 96 on the upper end of the frame 92. The other arm of the lever 95 is connected by a link 9! to the operating arm of a throttle valve 98 interposed in the steam supply piping 5| of the pump 45. Thus the operation and speed of the pump 45 are controlled according to the waterlevel in the boiler I5 and the demand on the latter for steam: i. e., when the demand increases and the water-level falls, more of the length of the tube 81 is in contact with hot steam, so that the tube expands and opens the valve 98, increasing the speed of the pump 45 and the rate of feedwater supply to the boiler in proportion to the increased demand for steam,--and vice-versa.

As shown in Figs. I, IV, and VI, the waterspace connection 89 of the regulator 80 is connected to one end of a horizontal equalizer tube I00 which extends and opens (through holes IOI) into the center of the upright cylindrical boiler shell I9. This makes the action of the regulator 86 as nearly as possible responsive to the quantitative or real average waterlevel in the upright cylindrical shell of the boiler I5, without regard to slope of the free surface of the water as affected by rapid acceleration or retardation of the train, or by super-elevation of the track on curves, etc. In the present instance, the equalizer tube I00 extends diametrally across the boiler I5, so that water-gauges and/or trycocks (not shown) may be connected to its other end, if desired, as indicated at I02 in Fig. I.

In case of failure of the regulator 86 to maintain an adequate waterlevel in the boiler |5, as by getting out of order, or because of failure of the water-supply to the pump 45,provision is made for shutting off fuel from the burner 30, by stopping the fuel pump motor 6|. For this purpose, there is a low-water cutout device I04 (Figs. I, IV, and VI) comprising a float I05 in a chamber I09 connected to the piping 89 and 9| leading to the water and steam spaces of the boiler. When the waterlevel in the boiler I5 falls unduly, the fall of the float I05 opens a valve I01 (Fig. I) and thus admits pressure from the chamber I00 through a pipe connection I08 to an automatic pressure-actuated cutout switch I09 controlling the power circuit of the motor 6|, thus stopping the pump 90. When rise of the waterlevel in the boiler I5 allows float I05 to close valve I01, pressure from the pipe I08 and the switch I 09 is exhausted through a bleed-port 0 and a drain tube (Figs. I and VI), allowing the power circuit to the fuelpump motor 6| to be automatically restored.

For additional protection against low water in the boiler I5, there is shown in Figs. I, VI, VII, VIII, and IX an automatic cut-out switch I|2 also controlling the power circuit of the fuel pump motor 6|, arranged to be normally closed until opened by an adjustable abutment or tappet H3 on the lever 95. When expansion of the regulator tube 8'I exceeds what may be considered a proper regulating range, however, the descent of the abutment I I3 opens the switch II2, thus stopping the fuel pump 60. There is also shown in Fig. I a thermal switch device II5 responsive to the temperature in the boiler stack 42, controlling the power circuit of the fuel pump motor 6!. This switch H5 is normally open until closed by rise of the stack temperature to a predetermined point. There is also a low-water alarm H6, consisting of electric bells and lights or the like, operated by closure of an automatic switch III in the alarm circuit. This switch II! is closed by descent of an abutment fork or tappet II8 on the lever 95 against locknuts adjustable on the switch stem IIQ when the regulator tube 81 expands beyond a proper limit, and opens when a proper waterlevel is restored.

There is also shown in Fig. I an automatic pressure-actuated switch I20 selectively controlling the operating circuits of the valve-controller 85, and connected by tubing I2I to the steamspace pipe connection 9|. Another control over the operation of the system is a pressure switch I22 connected to the fuel oil pipe line B'I from the pump 6|] to the burner 30, and normally open until closed by oil pressure due to the pump. In addition, there is an 'air relay I25 controlling the starting winding of the blower motor 34, and connected by a pipe I26 to the blower duct 33 leading to the boiler furnace. When pressure in the duct 33 falls, the relay I25 closes and causes energization of the starting winding, etc., of (induction) motor 34; but when the blower 32 speeds up, the resulting pressure in duct 33 opens the relay and causes the starting winding to be out out, so that the motor 34 may run normally, single phase.

Referring, now, to the wiring diagram in Fig. X as well as to the general scheme of the apparatus in Fig. I, the system and its operation may be further described and explained as follows:

Alternating current at some 220 v. (from the locomotive transformer, trolley, or third rail) may be used to run the blower motor 35, while for the fuel pump motor BI and the auxiliary and control circuits, direct current of low voltage (say 32) is preferred. For parts of the system where D. C. and A. C. circuits are in close proximity, the A. C. voltage may be stepped down to 24 v. (say) by means of a transformer. In Fig. X, the main circuits carrying A. C. at higher voltage are distinguished by the letter A, and those carrying A. C. at lower voltage by the letter a. As shown, a blower switch I33 serves to connect main circuit A including the blower motor 34 to the source of power at 220 volts A. C., and a transformer I3I serves to step down the voltage from circuit A to circuit a. Blower motor 34 is connected across circuit A, and also a circuit AI including starting winding I32 of motor 34, starting resistor E33, and starting contactor I34. Circuit a includes the solenoid winding E36 ofhigh flame relay with its double acting contactor I 31, as well as fuel oil pressure switch I22, and is controlled by single acting contactor I33 of a double starting switch I39.

Assume that the boiler I5 is cold and the pressure therein low, and that all the circuits and apparatus are deenergized. In starting up the boiler, the first step is to close blower switch I30, thus starting motor 34 split phase. As motor 34 comes up to speed, the resulting air pressure opens air relay switch I25 in the control circuit A2 of starting contactor I34, thus opening contactor I34 and cutting out winding I32 and resistor I33, and so throwing the motor over to single phase induction running.

The next step is to close the control switch Mil, thus connecting an auxiliary circuit to the low voltage D. C. power supply. This circuit 0 includes magnet winding I4I of pilot relay switch I42, and is completed through high flame relay switch I31 and the circuits 01 and control contactor I43 of valve controller I 54 as shown. This results in closing the pilot relay switch I42, without, however, closing any new circuits. Then the fuel pump motor switch I45 is closed, still without closing any new circuits or starting the pump motor 6!,- since fuel pump motor contactor I46 is open.

The next operation is to move the starting switch I39 to start, low flame position, thus closing its double acting contactor I48 to shunt stack control thermal switch II through a circuit D and so complete a control or pilot circuit d that includes the magnet winding I49 of the fuel pump motor contactor I46,and so close contactor I46. This closes and completes the power circuit e of the fuel pump motor 6|, so that the pump til operates to supply fuel under pressure through pipe line 61, closing fuel oil pressure switch I22. The fire is then lighted at burner 30, and the boiler I5 starts to heat up. The starting switch I33 is kept down in start, low flame position until stack control switch H5 heats up and closes, thus short circuiting circuit D and establishing circuit 01 independently, whereupon switch I33 may be released and returned to its run, low flame position as shown in Fig. X, with contactor I 48 bridging a different pair of contacts, and circuit D open. The system will then continue to run under low flame.

In order to allow of high flame operation, the starting switch I39 is thrown and latched up in run, automatic position, with its contacter 538 closed, thus c osing circuit a through winding I36 of high flame relay I31, and thereby shifting the contactor at 31 to its other pair of contacts. This short circuits the circuits 0% of the valve controller I44, and establishes circuit 0 independently thereof. In addition, it closes an air and fuel control circuit in shunt with a portion of circuit c, from high flame relay E31 through contactor I43, pressure control switch I2Il (in low pressure position as shown), valve controller operating circuits fl, contactor I58, and high flame field It! back to circuit 0. This energizes field H55 and so operates the motor of valve controller I 44 to throw the latter to high flame position, opening wide damper l5 and valves Ti and I8. It also opens contactors I43 and I513, thus breaking circuits c! and f, I and deenergizing high flame field IEI, and at the same time closes contactor I52 ready to energize low flame field I53 as hereinafter described. So long pressure control switch I20 remains in low pressure position as shown, valve controller I44 remains deenergized in the position to which it has been thrown as above described, and the system operates in high flame.

When, however, the boiler pressure rises sufficiently to throw pressure control switch I21) to high pressure position, the circuit 1 is closed through the valve controller operating circuits f2, contacto'r I52, and low flame field I53, thus energizing the latter and operating the motor of the valve controller I44 to throw the latter back to the low flame position shown, correspondingly closing damper l and valves 11 and T8 and thus returning the system to low flame operation. This continues until the boiler pressure drops sufficiently to return the pressure control switch I20 to low pressure position, when the valve controller motor is operated as before to change the system to high flame operation,and so on indefinitely as the boiler pressure fluctuates.

The operation of the various alarm and safety devices will be evident from the description already given, but may be briefly explained as follows:

If the water level in the boiler I5 falls too low, the regulator 86 will close the contacts II! and the alarm circuit g to operate the buzzers and light the lamps of the alarm H6, and will also open the low water cut-out H2 in the circuit d, thus deenergizing this circuit and causing the fuel pump motor contactor I46 to open the fuel pump power circuit e and stop the pump 60, and the pilot relay I42 to open the circuit 0. Stoppage of fuel pump 60 will cause the fuel oil pressure switch I22 to open, breaking the circuit a. and causing the high flame relay contactor at I3! to return to the position shown in Fig X. Eventually, also, the stack control switch H5 will open. Or, if the low water cut-out II2 fails to act, the auxiliary float device I64 will open the auxiliary low water cut-out IE9 with exactly the same effect. Or if the fire goes out for any reason, the absence of heat in the stack 42 will cause the stack control switch H5 to open with the same effect. Failure of the D. C. current supply to the switches 40, I45 will have the same effect as opening of one of the cut-outs I09, H2, H5.

On occasion (as on failure of current from the overhead trolley system), the regulatory mechanism can be operated by hand. For this purpose, the fulcrum pin I55 of the lever 80 (Fig. I) can be removed, and the lever 80 operated by hand according to the varying requirements for fuel and air. In this case, a draft may be created and maintained at the stack 42 by means of one or more exhaust and live steam and/or air jets I56, I51, supplied through valved pipe connections I58, I59 from the exhaust of the boiler feed pump 45 and from the boiler I5, Figs. II and IV. As shown, the live steam pipe I59 has a suitably valved connection I60 to the compressed air supply pipe 52.

Having thus described my invention, I claim:

1. The combination with a boiler of a safety device therefor responsive to the water level at the center of said boiler, and thus unaffected by variation in slope of the free surface of the liquid in the boiler.

2. The combination with an upright cylindrical boiler of a water-level responsive safety device therefor, and a water connection between said device and the boiler opening into the latter substantially at its vertical axis, so that said safety device shall respond truly to the quantity of water in the boiler, substantially unaffected by variation in slope of the free surface of the liquid in the boiler.

3. The combination with a boiler and means for supplying operating fluid thereto, of water level responsive means for controlling said operating fluid supplying means, and a water connection from said level-responsive means opening into the boiler substantially at its center, so that the operating fluid shall be controlled by the quantity of water in the boiler substantially unaffected by variation in slope of the free surface of the liquid in the boiler.

4. The combination with an upright cylindrical boiler and means for supplying operating fluid thereto, of water-level responsive means for controlling said operating fluid supplying means, and a water connection from said level-responsive means opening into the boiler substantially at its center and at a level approaching an oper ating supply of water in the boiler, so that said water-level responsive means shall respond directly to the level of water at the center of the boiler, substantially unaffected by variation in slope of the free surface of the water.

5. The combination with a boiler, means for supplying fuel to heat the boiler and for supplying energy to operate said fuel-supplying means, of circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supply of fuel by the aforesaid fuel supplying means, a circuit controlling the supply of energy to said fuel supply-varying means, and means responsive to the boiler pressure for controlling and reversing the action of said fuel supply-varying means.

6. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, and electrically driven means for supplying air for combustion of the fuel, of a circuit for supplying current to drive said air-supplying means, electrically operated means for varying the supplies of air and fuel by the aforesaid air and fuel supplying means, and means responsive to the boiler pressure for controlling and reversing the action of said air and fuel supply-varying means.

7. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, and electrically driven means for supplying air for combustion of the fuel, of electrically operated means for varying the supply of fuel by the aforesaid fuel supplying means, a circuit energized from said circuit that supplies current to drive said air-supplying means and controlling the supply of energy to said fuel supply-varying means, and means responsive to the boiler pressure for controlling and reversing the action of said fuel supply-varying means.

8. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supply of fuel by the aforesaid fuel supplying means, means responsive to the boiler pressure for controlling and reversing the action of said fuel supply-varying means, means for initially closing said control circuit, and means responsive to the heat of the fire for short-circuiting said lastnamed means and thus maintaining the control circuit closed regardless thereof.

9. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supply of fuel by the aforesaid fuel supplying means, a circuit controlling the supply of energy to said fuel supply-varying means, closing and opening means in said last-mentioned circuit responsive to pressure of the fuel supply, and means responsive to the boiler pressure for controlling and reversing the action of said fuel supply- Varying means.

10. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supply of fuel by the aforesaid fuel supplying means, a circuit controlling the supply of energy to said fuel supply-varying means, closing and opening means in said last-mentioned circuit responsive to pressure of the fuel supply, means for closing or opening said circuit when said last-mentioned means is closed, means responsive to the boiler pressure for controlling and reversing the action of said fuel supply-varying means, means for initially closing said control circuit, and means responsive to the heat of the fire for short-circuiting said last-named means and thus maintaining the control circuit closed regardless thereof.

11. The combination with a boiler, means for supplying and regulating fuel to heat the boiler and air for combustion of the fuel, and circuits for supplying energy to operate said fuel-supplying and air-supplying means, of a motorcontrol circuit including means for controlling energization of said motor supply circuit, and automatic cut-out means, with means for temporarily energizing said circuit at starting regardless of said cut-out means; an auxiliary circuit including means for controlling energization of said control circuit; an air and fuel control circuit including actuating means for the aforesaid fuel and air-regulating means; a circuit, whose energization is controlled by that of the air-supply means circuit, including means for controlling energizationpf said air and fuel control circuit; means responsive to the action of the fuel-supply means for controlling the lastmentioned circuit; and means responsive to the boiler pressure for controlling the action of the aforesaid actuating means.

12. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, and electrically driven means for supplying air for combustion of the fuel, of a circuit for supplying current to drive said air-supplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supplies of air and fuel by the aforesaid air and fuel supplying means, a circuit energized from said circuit that supplies current to drive said airsupplying means and controlling the supply of energy to said air and fuel supply-varying.

means, and means responsive to the boiler pressure for controlling and reversing the action of said air and fuel supply-varying means.

13. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, and electrically driven means for supplying air for combustion of the fuel, of a circuit for supplying current to drive said airsupplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supplies of air and fuel by the aforesaid air and fuel supplying means, a circuit energized from said circuit that supplies current to drive said air-supplying means and controlling the supply of energy to said air and fuel supplyvarying means, means responsive to the boiler pressure for controlling and reversing the action of said air and fuel supply-varying means, means for initially closing said control circuit, and means responsive to the heat of the fire for short-circuiting said last-named means and thus maintaining the control circuit closed regardless thereof.

14. The combination with a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, and electrically driven means for supplying air for combustion of the fuel, of a circuit for supplying current to drive said airsupplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supplies of air and fuel by the aforesaid air and fuel supplying means, a circuit energized from said circuit that supplies current to drive said air-supplying means and controlling the supply of energy to said air and fuel supply-varying means, closing and opening means in said last-mentioned circuit responsive to pressure of the fuel supply, and means responsive to the boiler pressure for controlling and reversing the action of said air and fuel supply-varying means.

15. The combination With a boiler, means for supplying fuel to heat the boiler, and for supplying energy to operate said fuel-supplying means, and electrically driven means for supplying air for combustion of the fuel, of a circuit for supplying current to drive said air-supplying means, circuits for controlling the supply of energy to operate said fuel-supplying means and for supplying energy to the control circuit, electrically operated means for varying the supplies of air and fuel by the aforesaid air and fuel supplying means, a circuit energized from said circuit that supplies current to drive said air-supplying means and controlling the supply of energy to. said air and fuel supply-varying means, closing and opening means in said last-mentioned circuit responsive to pressure of the fuel supply, means for closing or opening said circuit when said last-mentioned means is closed, means responsive to the boiler pressure for controlling and reversing the action of said air and fuel supply-varying means, means for initially closing said control circuit, and means responsive to the heat of the fire for short-circuiting said last-named means and thus maintaining the control circuit closed regardless thereof.

16. A boiler and furnace control system comprising a main circuit including a blower motor with its starting means; a circuit energized from said main circuit and including a control switch, a fuel oil pressure switch, and a contactor relay;

and air control circuit energized from said auxiliary circuit, controlled by said double contactor and including a reversible fuel and air supply motor operating said control contactor and provided with oppositely acting operating circuits and with means for opening and closing them on its opposite movements, and also including means responsive to boiler pressure for selectively controlling energization of said motor operating circuits.

ROBERT N. MILLER. 

